This is a postdoctoral training proposal for a basic scientist (Ph.D., lung toxicology) seeking expertise in state-of-the-art proteomics and metabolomics within a clinical pulmonary division, with the long-term goal of a research career in the mechanisms of lung disease. The proposal is significant to human health because it will systematically elucidate biological targets of hypothiocyanous acid (HOSCN) and hypochlorous acid (HOCl), major reactive chemicals formed during lung inflammation. HOSCN and HOCl are strong oxidants, taking electrons from antioxidants such as protein cysteine (Cys) residues thousands of times faster than hydrogen peroxide. However, HOSCN and HOCl differ in reactivity with specific Cys residues and cytotoxicity to multiple cell types. Furthermore, thiocyanate, which converts HOCl to HOSCN in vivo, improves outcomes of lung infection and inflammation in mice. Recent work demonstrated that thioredoxin reductase safely removes HOSCN but not HOCl in lung epithelia, causing cells exposed to HOSCN to be more viable than those given an equal dose of HOCl. This demonstrated that differential reactivity of HOSCN and HOCl with lung cell proteins could underpin the differences of their effects. Although several direct reactions have been studied, the critical targets of these oxidants in complex biological systems are uncertain, especially for HOSCN. This two-year proposal will take advantage of Emory University mentored training, environment and resources to produce impactful science. Two aims will investigate differential targeting of proteins and small molecules by HOSCN and HOCl in the lung using cell and animal models. Experiments will take advantage of well-developed mass spectrometry (MS)-based redox proteomic methods developed in the primary mentoring lab. This will be complemented with liquid chromatography-high resolution MS-based metabolomics, which gives unsurpassed measurement of metabolites in plasma, lung tissue and airway lining fluid. Scientific expertise and animal and cell resources in the Emory Center for CF and Airways Disease Research will be key components of the proposal aims. The proposal also takes advantage of training in integrated -omics techniques, national meetings and didactic training. This combination of academic environment, training and resources will build a sound foundation for the research career development of the applicant. The research resulting from this proposal will set a path for future translation of results into human studies. For example, human lavage fluid, sputum, tissue and plasma are collected at the Emory CF Bio-Repository and could be analyzed. Banked samples from the proposed studies will also provide for additional experiments not possible in the proposed time frame. This training and research plan will enable the applicant's continued development toward a successful independent research career in pulmonary biology and disease.